WO2010137384A1

WO2010137384A1 - Radiation detection device and method of manufacturing this device

Info

Publication number: WO2010137384A1
Application number: PCT/JP2010/054411
Authority: WO
Inventors: 秀樹星野; 寧中野; 尚大岡田
Original assignee: コニカミノルタエムジー株式会社
Priority date: 2009-05-29
Filing date: 2010-03-16
Publication date: 2010-12-02

Abstract

Provided are a high-sensitivity, high-resolution radiation detection device and a method of manufacturing an inexpensive and handy radiation detection device. The aforementioned radiation detection device and method of manufacturing a radiation detection device pertain to a method of manufacturing a radiation detection device having a plurality of fluorescent bodies which convert at least X-rays or γ-rays into visible light, as well as a plurality of light detection elements, and are characterized by comprising (i) a process where fluorescent precursors are filled into recesses which are formed in a light reflection film, which are enclosed by a light reflection material, and each of which is in one-to-one correspondence with one of the aforementioned light detection elements, (ii) a process where the aforementioned fluorescent precursors are caused to uniformly react in the recesses, thereby obtaining fluorescent bodies, and (iii) a process where fluorescent bodies in the aforementioned recesses are joined to the aforementioned light detection elements.

Description

Radiation detection apparatus and manufacturing method thereof

The present invention relates to a radiation detection apparatus having high sensitivity and high resolution and a method for manufacturing the same.

Conventionally, many proposals have been made on radiation detection devices using light detection elements and phosphors. As a high-sensitivity radiation detection device, for example, as disclosed in Patent Document 1, an intensifying screen is laminated as a phosphor layer and bonded to a photodetection element as a pixel two-dimensionally arranged on a substrate. An integrated radiation detection device is known. In the radiation detection apparatus, the radiation incident on the fluorescent plate is converted into visible light in the phosphor, is incident on each pixel of the light detection element while being uniformly scattered, and is converted into an electrical signal, whereby image characteristics are improved. can get.

The radiation detection apparatus disclosed in Patent Document 1 is manufactured by attaching and integrating a phosphor intensifying screen prepared by applying a phosphor on a support to a light detection element.

However, in the radiation detection apparatus manufactured in this way, the phosphor layer is made of a uniform phosphor, so that light that has been incident and converted into visible light also travels radially in the phosphor layer. In some cases, the light generated on the pixel is incident on an adjacent photodetecting element and the sharpness is impaired. In addition, in order to capture a large amount of radiation and convert it into visible light with a phosphor, it is required to make the thickness of the phosphor layer as thick as possible. When the thickness of the layer is increased, there is a problem that the sharpness is further deteriorated. In addition, the phosphor intensifying screen and the photodetector are bonded and integrated through an adhesive, so that the light generated from the phosphor is reflected and scattered by the adhesive and reaches the light detection element. In some cases, the amount of light decreased and the sensitivity decreased.

On the other hand, as a high-sensitivity and sharp radiation detection apparatus, for example, as disclosed in Patent Document 2, photodetection elements as pixels two-dimensionally arranged on a substrate, and corresponding to each of these pixels In addition, a radiation detection apparatus in which a phosphor embedded panel configured by embedding phosphors in a plurality of recesses formed on a substrate at a predetermined pitch is bonded and integrated in a state where the recesses and pixels correspond to each other in position. It has been known. Further, in this document, as a method for solving the above-described problem that the sharpness is impaired, a radiation detection apparatus in which a phosphor layer corresponds one-on-one for each pixel is disclosed. In the radiation detection apparatus, the radiation incident on the fluorescent plate is converted into visible light in the phosphor separated for each pixel, and the visible light generated for each separated phosphor layer is applied to each pixel of the light detection element. Incident light is converted into an electric signal, whereby high sharp image characteristics can be obtained.

The production of the radiation detection apparatus disclosed in the above-mentioned Patent Document 2 is performed by first preparing a substrate with a recess and filling the phosphor with a vapor deposition method or a melting method to form a phosphor-embedded panel, which is detected by light. A radiation detection apparatus is manufactured by bonding and integrating with the element. However, in such a radiation detection device, bubbles and microcracks are mixed when the phosphor is uniformly filled in the concave portion, and variations in sensitivity (sensitivity variations) of each detection element due to the mixture of bubbles and the like. , Non-uniform sensitivity distribution), low yield and high cost.

In Patent Document 3, as a method for improving the above-described mixing of bubbles or the like, radiation detection in which a scintillator having a uniform outer shape, which has been prepared in advance so as to conform to the shape of the recess, is inserted into the recess and joined to the adjacent isolation wall. An apparatus is disclosed.

However, in recent years, the required diagnostic performance has increased, and a high resolution of the photodetector has been demanded, and the pixel size of the photodetector element is desired to be 200 μm or less. Furthermore, in order to increase the rate at which radiation is converted into visible light by the phosphor as much as possible, it is required to make the phosphor layer as thick as possible. A scintillator having such a size and shape is inserted into the recess. In addition, it is very difficult and costly industrially to join the adjacent separating wall.

JP-A-9-145845 Japanese Patent Laid-Open No. 5-60871 JP-A-10-90420

The present invention has been made in view of the above problems and situations, and a problem to be solved is to provide a radiation detection apparatus with high sensitivity and high resolution, and an inexpensive and simple method for manufacturing a radiation detection apparatus. .

The above-mentioned problem according to the present invention is solved by the following means.

1. A method of manufacturing a radiation detector having a plurality of phosphors and light detection elements each for converting at least X-rays or γ-rays into visible light, and (i) a light reflection corresponding to each of the light detection elements on a one-to-one basis A step of filling a phosphor precursor in the recess of the light reflecting film having a recess surrounded by a material, and (ii) a step of uniformly reacting the phosphor precursor in the recess to obtain a phosphor, (Iii) A method for manufacturing a radiation detection apparatus, comprising the step of bonding the phosphor in the recess and the light detection element.

2. 2. The method of manufacturing a radiation detecting apparatus according to 1 above, wherein in the step of obtaining the phosphor by uniformly reacting the phosphor precursor in the recess, the reaction is performed while shielding the recess.

3. A radiation detection apparatus produced by the method for manufacturing a radiation detection apparatus according to 1 or 2 above.

By the above means of the present invention, it is possible to provide a radiation detection apparatus having high sensitivity and high resolution, and an inexpensive and simple method for manufacturing a radiation detection apparatus.

Conceptual diagram showing the structure of the radiation detector Conceptual diagram showing a means for forming a light reflecting film by applying glass paste to a screen mesh lattice pattern by screen printing and drying a plurality of times repeatedly The conceptual diagram which shows the method of filling the fluorescent substance precursor completely in a recessed part by repeating the process of removing a solvent after filling the fluorescent substance precursor solution in the concave part of the light reflecting film surface The figure which shows the example of an aspect which shields the recessed part upper part with a shield so that a fluorescent substance precursor may be enclosed

The manufacturing method of the radiation detection apparatus of the present invention is a manufacturing method of a radiation detector having a plurality of phosphors and photodetecting elements each converting at least X-rays or γ-rays into visible light, and (i) the light detection A step of filling a phosphor precursor in the concave portion of the light reflecting film having a concave portion surrounded by a light reflecting material corresponding to each of the elements, and (ii) uniforming the phosphor precursor in the concave portion And (iii) bonding the phosphor in the concave portion and the photodetecting element. This feature is a technical feature common to the inventions according to claims 1 to 3.

As an embodiment of the present invention, from the viewpoint of manifestation of the effect of the present invention, in the step of obtaining the phosphor by uniformly reacting the phosphor precursor in the recess, it is preferable that the recess is shielded and reacted. According to the manufacturing method of the present invention, a radiation detection apparatus having high sensitivity and high resolution can be obtained.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a structure of a radiation detection apparatus viewed from the side according to an embodiment of the present invention. In this radiation detection apparatus, the phosphor that is not covered with the light reflecting material of the phosphor layer 5 in which the phosphor 2 is formed in each concave portion of the light reflecting film 1 having a plurality of concave shapes surrounded by the light reflecting material. The two surfaces (lower part of the phosphor 2 in FIG. 1) and the light detecting element 3 provided in the light detecting layer 6 are joined and provided in a one-to-one correspondence.

Since the light emitted in the phosphor is reflected by the light reflecting layer, more light can be guided to the light detecting element (pixel). In addition, since light leaking to the adjacent photodetecting elements can be reduced as much as possible, a highly sharp image can be obtained.

The light reflecting film 1 makes light generated in the phosphor incident on each of the light detecting elements (pixels) corresponding one-to-one. The light reflecting film 1 may be a continuous lattice pattern or a discontinuous pattern such as a dot. May be formed. Further, the light reflecting film 1 may be formed as a single light reflecting material, or may be in a form in which only the portion in contact with the phosphor is surrounded by the light reflecting material using means such as vapor deposition or plating. The light reflecting material may be a reflective material that reflects visible light when the light generated in the phosphor layer is visible light. Specifically, aluminum, silver, silicon, white glass or the like is preferably used.

Further, if a light reflecting film such as a lattice pattern is formed of a phosphor, it not only functions as a pattern reflecting film but also functions as a light emitting film, so that higher sensitivity can be achieved.

Phosphor 2, for example, _{CsI (Tl), CsI (Na} ), CaF 2 (Eu), NaI (Tl), BGO _[Bi 4 _Ge 3 _O _{_{_12], CdWO 4, LiI (Eu)}} , BeF 2, CeF 3 And a scintillator material having a function of converting radiation such as X-rays and γ-rays into visible light. In addition, as a scintillator material, the organic scintillator material containing an aromatic compound can also be used.

The light detection element 3 is not particularly limited, and a solid-state imaging element such as a CCD or a CMOS is preferably used. Further, either an area sensor or a line sensor may be used.

Next, the manufacturing process of the phosphor layer 5 according to the present invention will be described with reference to FIGS. First, a light reflecting film is formed. The means for forming the recesses in the light reflecting film is not particularly limited, and various means such as nanoimprinting, dicing, sand blasting, and laser processing are used.

FIG. 2 shows means for forming a light reflection film by applying glass paste in a screen mesh lattice pattern by screen printing and drying a plurality of times. As shown in FIG. 2 (a), the glass paste 9 that has flowed out through the liquid retainer 8 is scanned with the squeegee 10 using the screen mesh 7 to produce the light reflecting film 1a in the middle of manufacturing, which is shown in FIG. 2), the reflective film 1 can be formed repeatedly as shown in FIG.

Next, the phosphor precursor is filled in the recess shown in FIG. The term “phosphor precursor” as used herein represents a raw material that constitutes the phosphor composition, and does not exhibit the characteristics of the phosphor itself, but adds some reaction means such as heat treatment to the phosphor precursor. By doing so, it becomes a phosphor. The method of filling the phosphor precursor is not particularly limited, and a method of filling powder particles, a solution in which the phosphor precursor is dissolved, or the like is preferably used.

3 shows an aqueous solution in which cesium iodide (CsI) and thallium sulfate (Tl ₂ SO ₄ ) are dissolved as the phosphor precursor solution 11 as shown in FIGS. 3 (b) and 3 (c). The process of drying and removing the solvent after filling in the recesses on the surface of the reflective film was repeated, and a method of finishing when the phosphor precursor 12 was completely filled in the recesses as shown in FIG. Is. Further, a powdered phosphor precursor 12 obtained by drying an aqueous solution in which cesium iodide (CsI) and thallium sulfate (Tl ₂ SO ₄ ) are dissolved to a desired particle diameter by means of spray drying or the like is formed into a concave portion by a vibrator. A method of filling the inside is also preferably used. At this time, the particle diameter of the phosphor precursor is preferably 1/5 to 1/200 of the diameter of the recess. Furthermore, the method of mixing the small particles and the large particles to fill the phosphor precursor in the recess Easy to make uniform.

Next, the phosphor precursor 12 completely filled in the recess is reacted uniformly in the recess to obtain a phosphor. In the present invention, it is preferable to react the upper part of the recess so as to surround the phosphor precursor 12 with, for example, one of the shielding objects 13a, 13b, or 13c illustrated in FIG. As shown in the shielding object (Example 1) 13a in FIG. 4A, each recess may be individually shielded with a single shielding object. Alternatively, the entire object may be collectively shielded by one piece as in the shielding object (Example 2) 13b in FIG. 4, or may be individually shielded for each recess as in the shielding object (Example 3) 13c in FIG. good. If the reaction is performed without shielding, the phosphor composition in the recesses is difficult to be uniform, and sensitivity variations occur between the surface and the bottom of the recesses, and the yield may be deteriorated or the emission luminance may be lowered. There is no particular limitation on the way of shielding, but it is desirable that the shielding is filled with phosphor as much as possible. Here, the reaction is not particularly limited, but generally indicates heat treatment. For example, heat treatment in an inert atmosphere at about 400 to 700 ° C. for 4 to 10 hours is preferably used for the reaction of the CsI: Tl phosphor. .

When the reaction is completed and the phosphor is obtained, the shielding object 12 is removed and bonded to a separately formed photodetection layer to complete the radiation detection apparatus. In the present invention, bonding refers to bonding with heat, an adhesive, or the like. Needless to say, it is necessary to align and bond the phosphor surface in the concave portion of the light reflecting film surface and the light detecting element in a one-to-one correspondence. It is preferable to perform alignment by enlarging with a CCD camera or the like so that the scintillator has a one-to-one correspondence with each of the light detection elements.

In addition, when the phosphor surface remains in a non-flat state by the above-described method, it may be bonded to the light detection layer after performing a flattening process by CMP (Chemical Mechanical Polish) or the like.

Hereinafter, the present invention will be specifically described with reference to examples, but the embodiment of the present invention is not limited thereto.

According to the following method, the radiation scintillator panels of Comparative Example 1, Example 1, and Example 2 were produced.

Comparative Example 1
A white glass paste was applied to a 50 cm × 50 cm glass substrate with a solid thickness of 30 μm and dried, and then applied by screen printing and dried using a screen with a mesh pattern of 254 μm pitch, openings 227 μm, and partition walls 27 μm. This was repeated for 12 layers. Thereafter, baking was performed in air at 550 ° C. to form a light reflecting film having a plurality of convex portions having an opening of 227 μm and a partition wall height of 450 μm.

After that, a powder in which CsI and TlI are mixed so as to be 1: 0.3 mol% is sprayed on the light reflecting film in an amount corresponding to the void volume in the concave portion, and then the melting point of CsI and TlI becomes 650 ° C. or higher. CsI: Tl scintillator panel 1 was obtained by melting and firing for 8 hours.

Example 1
A light reflecting film having a plurality of convex portions with openings of 100 μm and partition height of 450 μm is formed using a screen having a mesh pattern of 127 μm pitch, openings of 100 μm, and partition wall portions of 27 μm so as to be half the pitch of Comparative Example 1. did. Next, the light reflecting film was filled in an aqueous solution in which CsI and Tl ₂ SO ₄ were mixed at a concentration of 1: 0.3 mol%, and filled in the recesses. After that, as a result of evaporating water by vacuum drying, the dry powder was filled by 100 μm from the bottom of the recess, and thus the above-described operations from filling to drying were repeated 5 times. Next, the upper part of the light reflecting film filled with the dry powder in the concave portion was covered with a glass substrate and baked at 650 ° C. for 10 hours to obtain a CsI: Tl scintillator panel 2.

Example 2
A dry powder made by the same manufacturing method as in Comparative Example 1 is sealed with a glass substrate on the top of the light reflecting film filled in the void volume in the recess of the same light reflecting film as in Example 1. And firing at 650 ° C. for 10 hours to obtain a CsI: Tl scintillator panel 3.

(Create radiation detector)
PaxScan 2520 (Varian Medical Systems: pixel size 127 μm) was used as the light detection element, and the scintillator exposed surfaces of the scintillator panels 1 to 3 were bonded to the light detection element. At that time, after enlarging with a CCD camera, each photodetection element was aligned so that every other sample of Comparative Example 1 and the samples of Examples 1 and 2 corresponded one-to-one with the scintillator, Radiation detectors 1 to 3 were prepared by adhering and fixing the ends.

(Evaluation methods)
Luminance, image defects, and MTF were measured and calculated from the output data obtained for each sample of the radiation detectors 1 to 3 by the following method.

(Measurement of emission luminance)
X-ray with a tube voltage of 80 kVp is irradiated from the back of each sample (the surface on which the phosphor layer is not formed), and the amount of light emitted from the phosphor layer is detected and measured by the above-described photodetection element. The value was defined as “instantaneous light emission luminance (sensitivity)”. However, in Table 1, the value indicating the luminance is a relative value when the instantaneous emission luminance of the sample of Comparative Example 1 is 1.00. If the instantaneous light emission luminance is high, it can be said that the sensitivity is high. In Table 1, instantaneous light emission luminance is abbreviated as luminance.

(Image defect)
X-ray with tube voltage of 80 kVp is irradiated from the back of each sample (surface on which the phosphor layer is not formed), and the light emitted from the phosphor layer is detected and measured by the above-mentioned photodetection element. The number of defects in each pixel is measured. However, in Table 1, it is a relative value when a state having no image defect is 1.00. That is, when 10 image defects are recognized in 100 pixels, the relative value is 0.90.

(Calculation of MTF)
X-rays with a tube voltage of 80 kVp were irradiated from the back surface (surface on which the phosphor layer was not formed) of each sample through a lead MTF chart, and the image data was detected by a light detection element and recorded on a hard disk. Thereafter, the recording on the hard disk was analyzed by a computer to calculate the modulation transfer function (MTF (Modulation Transfer Function)) of the X-ray image recorded on the hard disk. The calculation results (MTF value (%) at a spatial frequency of 1 cycle / mm) are shown in Table 1 below. In the survey results in Table 1, the higher the MTF value, the better the sharpness.

As is apparent from the results shown in Table 1, according to the radiation detection apparatus of the present invention, the light converted into visible light by the phosphor 2 is converged without being diverged and enters the light detection element 3. Therefore, it is possible to realize a radiation detection apparatus having remarkably superior resolution and sensitivity as compared with the conventional radiation detection apparatus by an inexpensive and simple method.

DESCRIPTION OF SYMBOLS 1 Light reflection film 1a Light reflection film in the middle of manufacture 2 Phosphor 3 Photodetection element 4 Substrate 5 Phosphor layer 6 Photo detection layer 7 Screen mesh 8 Liquid retaining 9 Glass paste 10 Squeegee 11 Phosphor precursor solution 12 Phosphor precursor material 13a Shield (Example 1)
13b Shield (Example 2)
13c Shield (Example 3)

Claims

A method of manufacturing a radiation detector having a plurality of phosphors and light detection elements each for converting at least X-rays or γ-rays into visible light, and (i) a light reflection corresponding to each of the light detection elements on a one-to-one basis A step of filling a phosphor precursor in the recess of the light reflecting film having a recess surrounded by a material, and (ii) a step of uniformly reacting the phosphor precursor in the recess to obtain a phosphor, (Iii) A method for manufacturing a radiation detection apparatus, comprising the step of bonding the phosphor in the recess and the light detection element.
The method for manufacturing a radiation detection apparatus according to claim 1, wherein in the step of uniformly reacting the phosphor precursor in the recess to obtain the phosphor, the recess is shielded and reacted.
A radiation detection apparatus produced by the method for manufacturing a radiation detection apparatus according to claim 1 or 2.